This study was performed to investigate the effect of kangaroo care on body weight, physiological responses and behavioral states in premature infants. The subjects were 32 premature infants, fifteen for the kangaroo care group and seventeen for the control group, who hospitalized in a neonatal intensive care unit at a university-affiliated hospital. The kangaroo care was applied 8 times during the twenty five days with 40 minutes for each session. The kangaroo care provides the skin-to-skin contact during which a premature infant wearing a diaper and a hat is placed on its mother's chest. As for the measures, body weight was measured everyday. The levels of epinephrine, norepinephrine and 17-OHCS were measured twice, before beginning the first intervention and after finishing the last intervention. While each session of the care is undergoing, such physiological responses were measured periodically as heart rate, respiration rate, oxygen saturation, core temperature and skin temperature. The results were as follows : 1. The weight gain was significantly greater in the kangaroo care group than that in the control group during the period of performing the kangaroo care. 2. No significant difference was revealed between the two groups in heart rate, respiration rate, oxygen saturation and core temperature. The kangaroo care group also showed significant increases in the skin temperature. 3. The differences in the levels of epinephrine, norepinephrine and 17-OHCS were not significant between the kangaroo care and the control groups. The level of norepinephrine in the two groups was significantly increased over time. 4. Sleep pattern changed significantly in the kangaroo group from a very restless sleep to a very quiet sleep. These results suggest that kangaroo care is an effective nursing intervention for premature infants in gaining weight, achieving stable physiological responses and facilitating a quiet sleep.